How are the flybacks on a WG K7000 series monitor?

[MaximRecoil]

I noticed that flyback transformers are pretty cheap for a K7000. I'm going to be doing a capacitor kit on the monitor and I was wondering how the flybacks tend to be on these things, are they prone to failure? This monitor was manufactured in '86, so I was thinking that while I had the chassis out for the cap kit that it might be a good idea to change the flyback too.

Also, what about the HOT? Bob Roberts will throw in a HOT and a fuse for an extra $3 over what a cap kit + flyback costs; should I bother with that or is that overkill?

[Kevin Mullins]

The K7000 flyback seems to die abrubtly, so if you can afford it at least get one to have on hand. No real need to change it until it dies.
As for the HOT and fuse, they're just always good to have on hand.
It doesn't take much to wipe a HOT out by accident.
(the flyback dying could possibly take it out with it)

So I'd think you are better off getting it all if you can.

[Ken Layton]

The factory original flybacks are a high failure item. The aftermarket replacement flybacks are a million times better and I have never seen a replacement fail.

There's no need to replace a working horizontal output transistor.

[MaximRecoil]

Thanks for the replies.

I ordered the $26 kit from Bob Roberts yesterday which includes capacitors, a flyback, a HOT and a fuse.

And tonight, not long after Kevin Mullins said...

The K7000 flyback seems to die abrubtly

And Ken Layton said:

The factory original flybacks are a high failure item.

...I think the flyback finally gave up the ghost, right on cue. I turned on the machine a few minutes ago and heard a hissing sound coming from the monitor, and the picture went all screwy. I'm no monitor expert but that seems like a failed flyback to me...

[SirPeale]

Do you see sparks flying from the flyback?

[MaximRecoil]

Do you see sparks flying from the flyback?

I didn't have the back open when I last turned it on and got the hissing sound and screwy picture, so I don't know if there were sparks or not. The flyback does have a very noticeable crack in its housing, if that means anything (maybe not though, since the crack was there before it started hissing).

I'm not too keen on turning it on again until I've worked on the chassis. Bob Roberts cross-shipped the parts yesterday and said they should be here tomorrow or the next day.

It looks like an easy monitor to work on. I only see two screws to remove in order to pull the chassis (along with the usual other things that need to be disconnected of course). Last winter I did cap kits on my pair of Sanyo's in my Super Punch-Out machine, and changed the flyback on one of them, and those things are a pain to work on, so I'm guessing that this K7000 will be right neighborly in comparison.

[SirPeale]

K7000s are dead easy to work on.

When you change the flyback there is a resistor that *may* get in the way of one of the clips.  Don't worry about it...remove the clip.

[MaximRecoil]

Bob Roberts ships fast.

When I got the machine the main problem with the monitor was that the screen looked like the brightness was cranked up, but it would fluctuate between normal and too bright, but spend a lot more time on "too bright" than "normal".

Then the hissing thing started that last time I turned it on and the picture went completely screwy, like watching a scrambled cable channel or something.

I just finished installing the capacitor kit and the flyback ... I saved the new HOT and the fuse. Three or four of the larger capacitors had crusty, dried pools of leakage around them.

It is fixed now and the monitor is working perfectly; the only thing I had to adjust was the screen and focus pots on the new flyback, as they were both turned all the way to the left, and it was good.

One thing that I actually preferred when working on the Sanyo chassis was that the locations were marked on the solder side as well as on the parts side. The K7000 is only marked on the parts side.

[Ken Layton]

FYI, on all flybacks that have focus and screen controls built into it, you WILL need to adjust the screen and focus when you first power up.

[MaximRecoil]

FYI, on all flybacks that have focus and screen controls built into it, you WILL need to adjust the screen and focus when you first power up.

Yeah, both the focus and the screen pots were turned all the way counter-clockwise so I was expecting to have to adjust those.

I'm glad the tube was in good shape; this monitor now has bright vibrant colors over the whole range, and black blacks and white whites. The focus is nice and sharp as well. It displays like a new monitor. I'm very pleased with the results.

[SirPeale]

I just finished installing the capacitor kit and the flyback ... I saved the new HOT and the fuse. Three or four of the larger capacitors had crusty, dried pools of leakage around them.

I thought this was leakage myself when I first started this whole biz, but it's actually a glue.

[MaximRecoil]

I just finished installing the capacitor kit and the flyback ... I saved the new HOT and the fuse. Three or four of the larger capacitors had crusty, dried pools of leakage around them.

I thought this was leakage myself when I first started this whole biz, but it's actually a glue.

I thought it was glue when I first saw it ... but when I removed the ones that had it the bottoms seemed corroded/damaged so I figured it was leakage. They probably did leak some, hence the crustiness of the glue immediately around and on the base of them; as though something had chemically broken the glue down.

I wonder what the point of the glue was, other than to obscure the location and polarity markings?

[SirPeale]

I wonder what the point of the glue was, other than to obscure the location and polarity markings?

Keeps the part from shifting during movement.  Supposedly.

[MaximRecoil]

I wonder what the point of the glue was, other than to obscure the location and polarity markings?

Keeps the part from shifting during movement.  Supposedly.

Seems redundant to me, once soldered anyway.

I've been fiddling with the color/contrast and brightness settings, and I notice that when the picture looks perfect it shows moving retrace lines. I can turn the screen or brightness pot down enough so that I don't see them but then the picture is too dark. Is this a sync problem? On my Sanyo's in the Nintendo cabinet, if the screen or brightness pots are too high you see stationary retrace lines; and you can get the picture looking perfect (not too dark) by turning them down and you don't see the retrace lines at all. However, the retrace lines on this K7000 are not stationary, they cyclically scroll across the screen.

Also, the horizontal size of the picture is just a hair too big, so that about an eighth of an inch of the the edge of the picture is cut off. On a K7000, is that something that is determined by a capacitor value somewhere or is there an adjustment for it?

Edit: It looks like the value of C38 determines width according to this:



Edit #2: The retrace lines problem has been solved. Bob Roberts suggested that it was interference from the power supply, and that I should try subtracting earth ground from the monitor frame. This worked perfectly, and gave me a rock solid picture.